Locating devices

ABSTRACT

A device usable in a plurality of environments such as in buildings, transport vehicles, pedestrian aids and sirens for producing a locating sound of broad band noise. The broad band noise is formed from frequencies emitted simultaneously within a human hearing range. An alerting sound may also be emitted.

FIELD OF INVENTION

This invention relates to signal patterns for use in locating devices;locating devices; and systems incorporating locating devices for use in,particularly but not exclusively, buildings, domestic or commercial orlarge transport vehicles such as aircraft, liners or the like, or evenin pedestrian aids such as road crossing devices, and indicating devicessuch as audible warning devices or sirens and, particularly but notexclusively, vehicle sirens, or monitors such as security monitors.

In instances of emergency, or even in instances where it is simplynecessary to direct individuals to a predetermined location, audioand/or visual means may be provided in order to alert individuals to agiven situation and/or to indicate a direction in which individuals musttravel in response to said situation. For example, in the instance wherethere is danger or hazard because of a domestic or commercial fire or inthe instance where there is a leak either chemical or physical, such asin the form as radiation, it may be necessary to firstly alertindividuals to the potential danger or hazard and secondly to ensurethat the individuals can reach a safe environment. To this end, domesticdwellings or indeed any of the aforementioned constructions, may beprovided with smoke detectors and commercial buildings may be providedwith smoke/chemical/radiation detectors and a combination of signsindicating a safe point of exit. Activation of the detectors typicallyresult in a siren sounding which simply alerts individuals to potentialdanger and then individuals, either through knowledge of their owndomestic environment, or through following a number of signs areexpected to find a safe point of exit.

Unfortunately, where there is a fire or a chemical leak visual signs canbe used obscured from view and/or an individual's ability to see suchsigns can be impaired because of the effects of the smoke/chemical onvision. It therefore follows that the provision of a conventional alarmwith or-without signs is an insufficient safeguard to ensure thatindividuals can exit a building.

In addition to the above, in instances of danger or hazard, it may bedesirable for skilled personnel such as fire fighters or paramedics, toenter a building and in these situations it would be advantageous if ameans were provided for helping these people to navigate once inside thebuilding. Furthermore, it would also be extremely advantageous toprovide a means which enables skilled personnel in the building tolocate other skilled personnel. Such means do not currently exist.

In other instances of emergency for example, where a vehicle's siren issounding individuals may need to locate the siren and thus the vehiclein order to take evasive action. Whilst it is true to say thatindividuals may have learnt to recognise and respond to the soundpatterns generated by vehicles sirens such as those generated by policevehicles, ambulances or fire tenders it is not true to say thatindividuals can easily locate such vehicles, especially whilstundertaking another task e.g. whilst driving, and so be able to respond.This can be extremely problematical where an emergency service vehicleneeds to speed safely to the site of an incident. It therefore followsthat the provision of a siren which simply makes a loud noise, albeitthat the pattern of the noise may be distinctive, is not enough toensure that individuals can respond accordingly.

There are also many other instances where a device which facilitateslocalization could be used to advantage. For example, a burglar alarmthat was also adapted to enable localization would be advantageous; aidsfor the visually impaired and “earcons” to replace or complement theicons associated with computer software could also be provided with alocating means in accordance with the invention to considerableadvantage. It should therefore be apparent that although the inventionhas been described with reference to the above it has multipleapplications and indeed can be used in any situation where it isdesirable to provide an audio location device.

It is known that accurate sound localization is one of the mostcomplicated processes performed by the brain. Nethertheless, it is alsoknown that, given appropriate cues, the brain can detect the directionof a sound source up to an accuracy of 2°. This high degree of accuracyis only possible when the sound is complex and made up of a majority offrequencies in our hearing range. The brain can not locate, with anydegree of spatial precision, simple pure tones. Given this knowledge itis remarkable that for decades alerting sounds in common usage, in everyand any situation, for which directionality would seem an essentialcharacteristic, are not complex enough to permit accurate localization.In other words devices which are supposed to help us localise sounds donot possess the acoustic complexity necessary for accurate localization.

OBJECTS OF THE INVENTION AND BRIEF SUMMARY

It is therefore an object of the invention to provide an alarm, aid orearcon which enables an individual to locate a given object and takeappropriate action.

According to a first aspect of the invention there is therefore provideda device which is adapted to emit either simultaneously and/orsuccessively a locating sound comprising a majority of frequencies inthe human hearing range; and an alerting sound comprising a minority offrequencies within the human hearing range.

In a preferred embodiment of the invention the said locating soundcomprises either broadband noise or white noise or flat random noise.More preferably selected components of said noise are amplified orattenuated having regard to the properties of a speaker of the deviceand/or the absorbing properties of the environment in which a listeneris located and/or the auditory, either existing or expected, environmentof a listener.

For example, an emergency vehicle device is ideally adapted such thatfrequencies above 4 KHz are amplified either by selectively amplifyingfrequencies of 4 KHz or more and/or by selectively attenuatingfrequencies of less than 4 KHz such that vehicle drivers hear an optimumlocating sound, which is not deleteriously affected by the structure ofthe driver's vehicle and so has a relatively even spectral quality.

In a yet further preferred embodiment of the invention the said alertingsound comprises any suitable alerting or alarming noise either of aconventional nature or otherwise.

More preferably still said locating and alerting sounds are emittedsuccessively and ideally there is a predetermined interval between same.

More preferably further still said alerting sound comprises a number ofbursts of sound either of the same nature and duration or otherwise.

In the instance where the alerting sound comprises bursts of sound theinterval between each of said bursts may be identical or different andfurther more the interval between said bursts and said emission of saidlocating and alerting sounds may be identical or different.

Preferably at least one of said bursts and more preferably each of saidbursts of sound comprises a main fundamental frequency which in apreferred embodiment may be adapted to sweep over a frequency range. Thefundamental frequency of each of said bursts may be the same ordifferent so that in one example only of the invention a number ofsuccessive bursts of alerting sound are provided prior to and/or duringand/or after the emission of a locating sound.

In one embodiment of the invention there is provided a plurality of saiddevices wherein each device has a different but distinctive secondalerting sound. In this embodiment a selected skilled individual such asa fire fighter or paramedic is given one of the distinctive soundingdevices and a knowledge of this distinctive sound is conveyed to otherskilled personnel prior to the said individual entering a building. Inthis way a number of skilled personnel can be provided with distinctiveaudio signals that will enable other individuals, within the samebuilding, to firstly identify who, such as which class of personnel, isin the building, and secondly, where each of these individuals islocated.

The time intervals and the frequencies of said locating and alertingsounds and any intervals therebetween or therein are not crucial to theworking of the invention save only that an individual must be able tolocate a preselected device emitting said sounds and be alerted to theneed to do so or vice versa.

In a further aspect, the invention also relates to a locating devicewhich is adapted to emit locating sound comprising a majority offrequencies in the human hearing range at least one of which is selectedso as to be amplified or attenuated.

Ideally a plurality of such frequencies are selected as above so thatsaid device emits sound comprising at least one, and ideally a number ofamplified or attenuated frequencies.

In this preferred aspect of the invention said amplification orattenuation is performed having regard to the sound absorbing propertiesof the environment or medium through which the sound is to travel and/orthe auditory, existing or expected, environment through which the soundis to travel with a view to ensuring that a listener hears an optimumlocating sound and is thus able to locate the device.

More specific embodiments of the invention will now be provided by wayof example only in order that the reader may gain a clearerunderstanding of the invention, however it is not intended that thescope of the invention is to be limited in accordance with the followingexamples.

In one example of the invention said locating sound may be emitted foran interval between 1 ms and continuity however, in another embodimentof the invention we prefer to emit the locating sound for between 10 msto 2 secs and ideally between 10 ms to 500 ms, more preferably between150 ms and 300 ms or more preferably further still for a duration ofapproximately 200 ms.

The locating sound may be ramped so that, for example, a 5 ms onset timeis followed by 190 ms of sound emission and a 5 ms offset time. Althoughwe prefer a locating sound having the aforementioned ramped profileobvious alterations may be provided without deviating from the scope ofthe invention. We have found that ramping, advantageously, avoids aringing effect.

As an example only of locating sound broadband or white noise in a rangebetween 40 Hz and 20 kHz may be provided although in one embodiment weprefer to use 40 Hz to 16 kHz. However, it is not intended that theinvention should be limited to these frequencies which are merelyprovided by way of exemplification, rather any sound of sufficientcomplexity which enables localization can be used.

In so far as the alerting sound is concerned the duration may be between1 ms and an interval designed to attract the attention of an individual.In one embodiment of our invention we prefer to use a time interval ofbetween 1 ms and 100 secs and ideally we prefer an interval between 1 msand 200 ms, and further we prefer our alerting sound to comprise anumber of sound bursts, we prefer each burst to last for a duration ofbetween 1 ms and 100 ms and ideally between 20 ms and 30 ms and to beseparated by an interval of up to 50 ms and ideally of 10 ms. The numberand nature of bursts may be selected according to a user's requirements,for example we have found that a short interburst interval provides foran alerting sound of greater perceived urgency.

In some instances we prefer the alerting sound to also be ramped, againin order to avoid ringing and a startled response.

We prefer the nature of the alerting sound to comprise a fundamentalfrequency, we have used a frequency between 100 Hz to 3000 Hz andideally we prefer the frequency to be swept within a range between 100Hz to 2000 Hz and ideally between 400 Hz to 1200 Hz and more preferablyfurther still a frequency of approximately 500 Hz.

The fundamental frequency may be swept between a fundamental startfrequency and a fundamental finish frequency over the duration of thesignal burst, the sweep commencing at the fundamental start frequency atthe beginning of the signal burst and terminating at the fundamentalfinish frequency at the end of the signal burst.

Suitably, the fundamental frequency is swept between the fundamentalstart frequency and the fundamental finish frequency in a substantiallylinear manner.

The signal burst preferably comprises at least a first main frequency, asecond main frequency and a third main frequency. The first, second andthird main frequencies may each be swept during the duration of thesignal burst.

The first, second and third main frequencies may be swept in asubstantially linear manner between the start and the end of the signalburst duration.

The first main frequency is preferably of higher frequency than thefundamental frequency. The second main frequency is of higher frequencythan the fundamental and of higher frequency than the first mainfrequency. The third main frequency is higher than the fundamental,first or second main frequencies at any instance during the sound burst.

A said main frequency may comprise a harmonic of the first frequency. Afirst main frequency may comprise a first at least one harmonic of thefundamental frequency. A second main frequency may comprise a second atleast one harmonic of the fundamental frequency. A third main frequencymay comprise a third at least one harmonic of the fundamental frequency.

As the fundamental frequency is swept between the fundamental startfrequency and the fundamental finish frequency, the first main frequencymay be swept between a first start frequency and a first finishfrequency. The first start frequency may be a harmonic frequency of thefundamental start frequency. The first finish frequency may be anharmonic frequency of the fundamental finish frequency.

The second and third main frequencies may be swept between respectivesecond and third start frequencies and second and third frequencies.

By providing a plurality of main frequencies each of which are swept infrequency as the fundamental frequency is swept, and which therebymaintain at any instant during the sound burst, a harmonic relationshipbetween the fundamental frequency and the first, second and third mainfrequencies, a distinctive burst of sound may be produced which thehuman brain finds to be alerting.

However, by selecting the first, second and/or third main frequencies tobe away from harmonics of the fundamental frequency, a burst of soundcan be produced which although unpleasant to the human ear, is equallydistinctive and alerting.

Preferably the alerting sound is repeated a plurality of times. Suitablyan alert signal burst is produced, and then after a first delay, anotheralert signal burst is produced and then, after a second delay, anotheralert signal burst is produced.

Preferably the first and/or second delays each have a duration in therange 5 ms to 100 ms. Optimal delay times have found to be of the orderof 10 ms, or of the order of 50 ms.

Preferably after the final alert signal burst, there is a third delay,followed by the noise burst.

When a signal pattern of this type is applied to a siren, or other soundgenerator, the siren produces three alerting sound bursts, repeated inseries, followed by a locating sound burst. This may have the effect ofinitially alerting a hearer to the presence of the siren (the alertingsound burst), and then enabling the hearer to judge the direction of thesiren (by listening to the locating sound burst).

The selection of a fundamental frequency can be varied along with theassociated harmonics according to a user's requirements.

Moreover, the relative level of each harmonic may be varied to providean alerting sound of selected timbre.

In yet further preferred embodiments of the invention the said devicesare provided with a cut-out means which after a preselected interval oftime disables at least the locating sound.

The advantage of this embodiment of the invention is that it ensuresthat individuals will not travel towards a site of danger but willmerely be alerted to the need to take action. Ideally the said intervalof time can be adjusted having regard to the nature of the environmentin which the device is to be located. For example, in the instance wherea fire has occurred and an environment is thought to comprise highlycombustible items then the cut-out interval will be short, or at leastshorter than an interval selected for an environment where there areknown to be no combustible items and where there may also be an escapeexit.

Alternatively the cut-out means may be activated once aheat/chemical/radiation detector, or other detector, associated with thedevice records a preselected level of a corresponding indicator such assmoke, chemicals, radiation etc.

In this preferred embodiment of the invention after a suitable instancein time said cut-out means may also disable the alerting means. In thisinstance individuals may be advised to travel towards noise and ideallytowards locating noise.

Ideally the said device also includes or is associated with a camera orrecorder such as, for example, in a security system where an image of anintruder is required and the device thus included means to prompt theintruder to look toward said camera or recorder.

According to a second aspect of the invention there is provided a devicefurther comprising at least first and second devices each adapted toemit at least one, and in totality both of said locating and alertingsounds, and further wherein said device comprises a control means forcoordinating the emission of said locating and/or alerting sounds eithersimultaneously or successively.

The device of the invention may include any of the features eithersingularly or in combination afore described.

According to a yet third aspect of the invention there is provided asignal pattern comprising a locating and alerting sound in accordancewith the invention.

According to a yet fourth aspect of the invention there is provided asiren for an emergency vehicle, wherein the siren is adapted to emit asound signal comprising; an alerting sound, and a locating sound phase.

Ideally the alerting sound comprises a plurality of sound bursts, eachsound burst comprising a fundamental frequency which is swept over afrequency range within a respective duration of each sound burst.

Ideally the locating sound comprises a majority of frequencies in thehuman hearing range and ideally broadband noise.

Suitably, the alerting sound phase is of total duration in the range 250ms to 600 ms, and suitably in the range of 370 ms to 450 ms.

Preferably the locating sound phase is of total duration in the range 10ms to 500 ms, and suitably around 200 ms to 250 ms.

An emergency vehicle siren producing a generated sound pattern asdescribed above may reduce the number of accidents involving emergencyvehicles, and reduce journey times for emergency vehicles, particularlythrough heavy traffic.

The invention includes a sound generating means arranged to receive anaudio signal pattern as described with reference to the above aspects.

The invention includes a signal generating means adapted to produce anaudio signal or an audio signal pattern or a sound as described by theabove aspects.

The invention includes a signal storage means adapted to carry an audiosignal or signal pattern signal as described by the above aspects.

The invention will now be described by way of example only in order thatthe reader may more readily understand the nature of the device, system,signal pattern and siren in accordance with the invention. However, itis not intended that the scope of the invention should be limited by thefollowing information which is provided by way of exemplification only.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a general representation of an audio signal burst of afirst duration, for producing an alerting sound;

FIG. 2 shows another audio signal burst of a second duration, forproducing a locating sound;

FIG. 3 shows a first signal pattern;

FIG. 4 shows a second signal pattern;

FIG. 5 describes in chart form the second alert signal burst of Table 2.

Table 1 describes a first specific alert signal burst;

Table 2 describes a second specific alert signal burst;

Table 3 describes a third specific alert signal burst;

Table 4 describes a fourth specific alert signal burst;

Table 5 describes a fifth specific alert signal burst;

Table 6 describes a sixth specific alert signal burst;

Table 7 describes a seventh specific alert signal burst;

Table 8 describes a eighth specific alert signal burst; and

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 to 5 of the accompanying drawings and Tables 1 to 8 of theaccompanying tables describe specific audio signals and audio signalpatterns, which may take the form of electronic signals fed to a sirenor other like sound generating means. A sound produced by the siren orother sound generating means will contain substantially the samefrequency and amplitude components, but rather than in electric signalform, will be in the form of a pressure wave in air, or other likemedium which surrounds the siren/signal generating means.

Referring to FIG. 1 of the accompanying drawings, there is shown analert signal burst 1. The alert signal burst 1 comprises a 100 ms burstof audio signal having a 2 ms leading edge, or rise time, 2, in whichthe signal is raised from a low amplitude level corresponding to aninaudible sound, to a high amplitude level corresponding to a loudaudible sound, and a 2 ms falling edge, or fall time, 3 in which thesignal falls from its high amplitude level, to its low amplitude level.

The alert signal burst of FIG. 1 is intended to produce a sound whichimmediately commands the attention of a listener in the vicinity of thesiren sound signal generator means.

Referring to FIG. 2 of the accompanying drawings, there is shown alocating audio signal burst comprising a 190 ms burst of white noise,having a 5 ms leading edge in which the white noise signal or broadbandnoise in the range 40 Hz to 4 kHz, which undergoes an amplitudetransition from a minimum amplitude level in which the signal producesan inaudible, or barely audible sound or no sound to maximum amplitudelevel, and 5 ms trailing edge, in which the signal undergoes transitionfrom its maximum level to its minimum level.

The locating audio signal burst of FIG. 2 is intended to allow locationof the sound generator by a listener, e.g. the siren, emitting a soundin accordance with the audio signal burst of FIG. 3.

It has been found experimentally that a human listener may more easilylocate a broadband noise sound signal than a monotone or polytone signalcomprising a few frequencies. The human brain is capable ofdistinguishing the direction from which a broadband sound, e.g. whitenoise sound emits, taking account of reflections from obstacles, etc.and background noise.

Referring to FIG. 3, there is shown a first audio signal pattern. Thefirst audio signal pattern comprises an alerting phase 30, comprising aplurality of successive alert pulses 31, 32, 33, the alert pulsesrepeated one after each other, with a 10 ms silence between the finishof a preceding alert pulse and commencement of a successive alert pulse;and a localizing phase 40 in which a localizing audio signal burst 34 isprovided. At the end of the alerting phase, a 50 ms silence is providedbefore commencement of the locating phase. The duration of thelocalizing audio signal burst 34 is predetermined, and may be in therange 100 ms to 400 ms and optimally, around 200 ms. The localizingsignal burst 34 is separated by the silent period of 50 ms, from thepreceding alert signal burst 33.

After the localizing signal burst 34 there is a 50 ms silence at the endof the localizing phase 40 prior to repeating the alerting phase 30 of asubsequent signal pattern.

It is found experimentally that by repeating an alert sound burst threetimes, with a slight delay between bursts, and then, after a furtherdelay consulting a locating sound burst, a human listener is placed inan attentive state by the alert sounds and then locates the directionfrom which the sounds are coming, by hearing the locating sound.

The alert signal bursts 31, 32, 33 in the alerting phase 30 may eachcomprise respective fundamental, first, second and third main frequencycomponents F_(F), F1, F2, F3. Each of the main frequency components maybe present in the alert pulse in varying amplitude proportions.

For example another second alert signal burst is described in Table 2 ofthe accompanying tables. The second alert signal burst comprises afundamental frequency component F1 commencing at 600 Hz and rising overa 500 Hz frequency sweep, to 1100 Hz.

In the second signal alert burst as described in Table 2, there arepresent four frequency components comprising a fundamental, and first,second, and third harmonics of the fundamental. As the fundamentalsweeps in frequency over the duration of the alert pulse, the first,second, and third harmonics similarly sweep in harmonic relation to thefundamental.

In the second alert signal burst, the fundamental frequency F₀ whichsweeps over the duration of the alert pulse at a start frequency of 600Hz, over a 500 Hz range to 1100 Hz. The first main frequency F1 elementsweeps between 1200 Hz and 2200 Hz over the duration of the alert signalburst. The second main frequency element F2 sweeps between 1800 Hz and3300 Hz over the duration of the alert signal burst. The third mainfrequency component F3 sweeps from a start frequency of 2400 Hz to afinish frequency of 4400 Hz over the duration of the alert signal burst.

Respective third and fourth alert signal bursts are described in Tables3 and 4 of the accompanying tables. Each of the third or fourth alertpulses may be repeated in the alerting phase of a sound pattern, with 10ms silent periods between successive alert signal burst, and with a 50ms silence between the end of the final alert signal burst and thecommencement of the locating signal burst 34.

Referring to Table 3, the third alert signal burst comprises afundamental frequency component of 400 Hz carrier frequency, whichtravels over a 500 Hz frequency sweep to raise to 900 Hz at the end ofthe 100 ms duration of the alert signal burst.

There may be provided first, second and third main frequency componentsF1, F2, F3 respectively which in the third alert pulse are present inequal amplitude to each other.

The fourth alert signal burst as described in Table 4, comprises a firstfrequency component F1 of 600 Hz, modulated by 500 Hz sweep to raise to1100 Hz over the 100 ms duration of the signal burst. A first mainfrequency component F1 sweeps in the range 1200 Hz to 2200 Hz, a secondmain frequency component F2 sweeps in the range 1800 Hz to 3300 Hz, anda third main frequency component F3 sweeps in the range 2400 Hz to 4400Hz. The fundamental and first to third main frequency components arepresent in equal amplitude proportion, i.e. in the proportion F_(F)F1:F2:F3=0 dB:0 dB:0 dB:0 dB.

The fundamental, the first second and third main frequency componentsF_(F), F1, F2, F3 respectively may be present in the ratioF_(F):F1:F2:F3:=0 dB:−3 dB:−6 dB:9 dB.

Referring to Table 8, an eighth alert signal burst which may be used inalerting phase 30, comprises a main fundamental frequency componentF_(F) swept from 600 Hz to 1100 Hz over the 100 ms duration of the alertsignal burst 30; a first main frequency component F1 comprising a sweptfrequency signal beginning at 800 Hz and swept to 1467 Hz over theduration of the alert signal burst 30; a second main frequency componentF2, commencing at 1000 Hz and swept to 1833 Hz over the duration of thealert signal burst 30, and a third main frequency component F3,beginning at 1200 Hz and swept upwardly in frequency to 2200 Hz over theduration of the alert signal burst 30. The main frequency componentsF_(F), F1, F2, and F3 are present in the eighth alert signal burst ofTable 8 in the ratio as follows; 0 dB:0 dB:0 dB:0 dB i.e. present inequal amplitude proportions to each other.

In the eighth alert signal burst of Table 8, the first second and thirdmain frequencies do not lie on harmonics of the fundamental frequency.The ratio of FF, F1, F2 and F3 is maintained at approximately1:1.33:1.666:2.0 throughout the frequency sweep and throughout theduration of the alert signal burst.

Further examples of alert signal burst are described in Tables 1 and 5to 7 of the accompanying tables.

The sound pattern of FIG. 3 is fed to a sound generating means, e.g. asiren to produce a sound which is played through the siren of, forexample, an emergency vehicle and which has substantially the samefrequency characteristics as the sound pattern of FIG. 3.

In experimental tests, the signal of FIG. 3 was supplied to a broadrange speaker, and the output of the speaker measured using an SPLmeter. The speaker running at 2,400 revs per minute produced a 63 dB(A)rms signal, having a 77 dBa peak. The signal of FIG. 3 was measured at52-64 dB(A) rms, (69-77.5 dB (A) peak).

Under experimental conditions, eight broad range speakers were used andwere found to produce peak signals to within ±3 dB(A) of each other. Thesignals were measured against a background of white noise to test theiraudibility against the white noise background.

Referring to FIG. 4, there is shown a second signal pattern comprisingan alerting phase 50, the alerting phase comprising a series of alertsignal bursts 51-53 played sequentially, with 50 ms silences betweensuccessive alert signal bursts, followed by a 50 ms silence at the endof the alerting phase; and a localizing phase 60 comprising one or aplurality of localizing signal bursts 54 played in series and separatedby each other by a 50 ms silence.

Any one or more, or any combination of the aforementioned signalpatterns may be feed through a sound generating means in any of thedevices for which the invention has application. For example the soundpattern may be feed to an alarm, an aid, or an earcon or indeed or anyother device where location of an object in an alerting situation isimportant.

Although the invention has been described by reference to a single soundgenerating means the invention also comprises a system where a pluralityof sound generating means are provided and either first and second soundgenerating means are adapted to emit first and second sounds i.e.locating sounds and alerting sounds respectively; or alternatively asystem where a plurality of sound generating means are adapted to emitboth said first and second sounds in a controlled manner so that thenature and duration of said sounds can be predetermined and theinteraction of each of one or more of said devices may be controlled soas to provide for a preselected sound pattern which represents thetotality of the sound emitted from all or selected ones of said devices.

In the instance where the invention is to be used in relation to a fixedstructure such as a building the locating sound may comprise bursts oflocating noise wherein the interval between each of said burstssuccessively diminishes and/or the length of each burst of locatingnoise successively diminishes thus providing for a noise pattern ofquickening sound or continuity.

The invention thus provides for a sound device having the followingadvantageous properties:

(i) The sound is relatively unaffected by reflections or echoes of thesound from buildings etc.

(ii) The sound allows a person hearing the sound to estimate thedistance of the object from which the sound emanates.

(iii) In the instance where the invention is embodied in a vehicle sirenthe identification of vehicle speed, vehicle type, vehicle location ispossible.

(iv) The sound can be adapted so as to be easily distinguishable fromfire alarms, car alarms, or burglar alarms in the vicinity of thevehicle.

(v) The sound is easily distinguished from and stands out from generalbackground noise, street noise, passing aircraft etc.

(vi) The sound enables a person hearing the sound, to estimate thedirection relative to the person from which the sound is coming from.

(vii) The sound immediately alerts a person who hears the sound.

(viii) The sound may enable a person hearing the sound to identify theparticular type of vehicle, e.g. police car, ambulance, fire engine towhich the sound relates.

(ix) In the instance where the invention is embodied in a device orsystem for location in a building, the sound enables the person hearingthe sound to navigate safe route of entry/exit.

(x) In the instance where the invention is embodied in a burglar alarmthe sound enables the person hearing the sound to detect the location ofthe alarm and thus the burgled site.

(xi) In the instance where the invention is embodied in an aid for thevisually handicapped the sound enables the person hearing the sound tonavigate.

(xii) In the instance where the device includes or is associated with acamera or recorder the device ensures that a suitable image of anintruder is recorded.

Other advantageous properties of the invention will be apparent to thoseskilled in the art and to those who have experience of the invention.

TABLE 1 Burst 50 F1 400 Hz with 500 Hz sweep. (type 2) 10 mS interpulsegap alerting phase. 50 mS alerting - locating F1 400 Hz ˜ 900 Hz @ 0 dBF2 800 Hz ˜ 1800 Hz @ −3 dB F3 1200 Hz ˜ 2700 Hz @ −6 dB F4 1600 Hz ˜3600 Hz @ −9 dB F5 2000 Hz ˜ 4500 Hz @ −12 db Where F1 is thefundamental frequency

TABLE 2 Burst 51 F1 600 Hz, 500 Hz sweep. (type 1) 10 mS interpulse gapalerting phase. 50 mS alerting - locating F1 600 Hz ˜ 1100 Hz @ 0 dB F21200 Hz ˜ 2200 Hz @ 0 dB F3 1800 Hz ˜ 3300 Hz @ 0 dB F4 2400 Hz ˜ 4400Hz @ 0 dB Where F1 is the fundamental frequency

TABLE 3 Burst 52 F1 400 Hz, 500 Hz sweep. (type 1) 10 mS interpulse gapalerting phase. 50 mS alerting - locating F1 400 Hz ˜ 900 Hz @ 0 dB F2800 Hz ˜ 1800 Hz @ 0 dB F3 1200 Hz ˜ 2700 Hz @ 0 dB F4 1600 Hz ˜ 3600 Hz@ 0 dB Where F1 is the fundamental frequency

TABLE 4 Burst 53 F1 600 Hz, 500 Hz sweep. (type 1) 10 mS interpulse gapalerting phase. 50 mS alerting - locating F1 600 Hz ˜ 1100 Hz @ 0 dB F21200 Hz ˜ 2200 Hz @ −3 dB F3 1800 Hz ˜ 3300 Hz @ −6 dB F4 2400 Hz ˜ 4400Hz @ −9 dB Where F1 is the fundamental frequency

TABLE 5 Burst 42A F1 600 Hz, 500 Hz sweep. 50 mS interpulse gap. (type2) F1 600 Hz ˜ 1100 Hz @ 0 dB F2 1200 Hz ˜ 2200 Hz @ −3 db F3 1800 Hz ˜3300 Hz @ −6 dB F4 2400 Hz ˜ 4400 Hz @ −9 dB

TABLE 6 Burst 42BC F1 600 Hz with 500 Hz sweep. 50 mS interpulse gap.(type 2) F1 600 Hz ˜ 1100 Hz @ 0 dB F2 1200 Hz ˜ 2200 Hz @ 0 dB F3 1800Hz ˜ 3300 Hz @ 0 dB F4 2400 Hz ˜ 4400 Hz @ 0 dB

TABLE 7 Burst 46 INHARMONIC. 50 mS interpulse gap, equal amplitude.(type 2) F1 600 Hz swept to ..1100 HZ, Fa 900 Hz swept to 1650 Hz Fb1200 HZ swept to 2200 Hz, Fc 1500 Hz swept to 2750 Hz

TABLE 8 Burst 47 INHARMONIC. 50 mS interpulse gap, equal amplitude.(type 1) F1 600 Hz swept to 1100 Hz @ 0 dB Fa 800 Hz swept to 1467 Hz @0 dB Fb 1000 Hz swept to 1833 Hz @ 0 dB Fc 1200 Hz swept to 2200 Hz @ 0dB

What is claimed is:
 1. A directing and alerting device which is adaptedto emit either simultaneously or successively a locating soundcomprising broad band noise formed from frequencies emittedsimultaneously and falling within a human hearing range between 40 Hzand 20 kHz; and an alerting sound comprising at least one frequencywithin the human hearing range.
 2. A device according to claim 1 whereinsaid locating sound comprises white noise or a flat random noise.
 3. Adevice according to claim 1 wherein said locating sound comprises atlease one selected frequency which is either amplified or attenuated..4. A device according to claim 1 wherein said locating and alertingsounds are emitted successively.
 5. A device according to claim 4wherein there is a predetermined interval between said emissions.
 6. Adevice according to claim 1 wherein said alerting sound comprises aplurality of bursts of sound.
 7. A device according to claim 6 whereinthe interval between said bursts is predetermined.
 8. A device accordingto claim 6 wherein the interval between said bursts of alerting soundand said locating sound is predetermined.
 9. A device according to claim6 wherein at least one of said bursts comprises a main fundamentalfrequency.
 10. A device according to claim 9 wherein said fundamentalfrequency sweeps over a frequency range.
 11. A device according to claim6 wherein at least two of said bursts are of different frequency.
 12. Adevice according to claim 1 wherein said alerting sound is emitted priorto said locating sound.
 13. A device according to claim 1 wherein saidalerting sound is emitted after said locating sound.
 14. A deviceaccording to claim 1 wherein said alerting sound comprises at least twodistinctive components.
 15. A device according to claim 1 wherein saidalerting sound is ramped.
 16. A device according to claim 1 furthercomprising a cut-out means which after a preselected interval of timedisables or cuts-out at least the locating sound.
 17. A device accordingto claim 1 further comprising a cut-out means which following selectiveactivation disables or cuts-out at least the alerting sound.
 18. Adevice according to claim 1 wherein said device further includes or isassociated with a camera or a records.
 19. A device according to claim 1wherein said device further comprises at least first and second deviceseach adapted to emit at least either the locating or the alerting sound,and further wherein said device comprises a control means forcoordinating the emission of said locating and/or alerting sounds eithersimultaneously or successively.
 20. A device according to claim 1wherein said device is provided with amplification and/or attenuationmeans for selectively amplifying or attenuating at least one frequencycomponent of said locating sound.
 21. A device according to claim 1comprising a signal generating means for generating a locating sound ora locating sound and an alerting sound.
 22. A device according to claim1 comprising a signal storage means in which there is stored an audiosignal comprising a locating sound or a locating sound and an alertingsound.
 23. A device which is adapted to emit a locating sound comprisingbroad band noise formed from frequencies emitted simultaneously andfalling within a human hearing range between 40 Hz and 20 kHz.
 24. Adevice according to claim 23 wherein said broad band noise is emittedfor a time period between 10 ms and 2 secs.
 25. A device according toclaim 23 wherein the broad band noise is ramped.
 26. A device accordingto any one of claims 23, 24, or 25 wherein broad band noise in a rangebetween 40 Hz and 20 kHz is provided.
 27. A device according to claim 23wherein broad band noise in a range between 40 Hz to 16 kHz is provided.28. A device comprising signal generating means comprising means forgenerating a locating sound comprising a burst of broad band noisecovering a majority of frequencies emitted simultaneously in the humanhearing range within 40 Hz and 20 kHz.
 29. A device comprising signalgenerating means according to claim 28 wherein said means generatefrequencies comprising said broad band noise simultaneously.
 30. Adevice comprising signal storage means in which there is stored an audiosignal comprising a locating sound comprising a burst of broad bandnoise covering a majority of frequencies emitted simultaneously in thehuman hearing range within 40 Hz and 20 kHz.